Optical image stabilization (OIS) is a useful technology for providing improved image quality when images are taken by a camera that is shaking or otherwise not stationary. For example, cameras mounted on moving objects (e.g., cars, bicycles, helmets) or held by a person with in an outstretched arm (e.g., FIG. 1) are able to capture clearer, better focused images by utilizing OIS technology to counteract vibrations, shaking, and other motion of the camera. One type of OIS, known as “tilt OIS,” is accomplished by pivoting or tilting the camera in response to the sensed motion of the structure to which the camera is mounted, allowing the camera to remain pointed in the desired direction and maintain a desired focus. Auto-focus (AF) technologies can also be used in conjunction with tilt OIS to provide images with better focus properties.
Sometimes it is desirable to capture images where part of the image is in focus and another part of the image is intentionally out of focus. This can be referred to as a “depth of field effect.” Some depth of field effects are known as “bokeh effects.” Bokeh typically refers to the appearance of the out of focus portions of an image, such as a blurry, blotted, or swirly appearance of a background located behind the focus plane that includes the primary object of the image. Photographers often deliberately use bokeh or other depth of field effects to create images with prominent out of focus regions with desired aesthetic qualities.
Typical mobile phone cameras have small lenses and small image sensors, with a limited depth of field range, and thus are often not optically able to create naturally beautiful bokeh effects, or other similar depth of field effects. Tilt OIS technology in combination with AF technology can be used in mobile phone cameras and other small cameras to create such a shallow depth of field effect, but only on one axis due to the optical distortion created by tilt of the lens stack and natural one axis shallow depth of field. This is known as the Scheimpflug principle. A typical use of this principle, e.g., in landscape photography, is to tilt the lens sufficiently to keep both near and far in focus with a single image. However, this does not help when it is desired to create an image with a depth of field effect where part of the image is to be in focus and another part is to be starkly out of focus, as in bokeh. A further problem with typical tilt based blur is that due to the optical effect, the shallow depth of field shape is wedge shaped. This makes it very difficult to use it for generic images, and care must be applied in choosing how this sharp depth of field passes on the subjects.